Hi Wolf, If it makes you feel better, you could apply the inverse transform to your surface coordinates (see Window: Transformation Matrix Editor or caret_command -surface-apply-transformation-matrix), so that you can map your Z-map directly to the "native" surface.
I hope others speak up if they disagree with me, but reporting interpolated z-values should be pretty far down on your stack of things to worry about. It would be different if this were a label/ROI file you were mapping, but then you would use nearest neighbor (NN). Of course, that is another alternative -- using NN for your Z-map. But I'm guessing these are bigger fMRI sized voxels, so there are concerns there. I think you'll sleep better if you bring your surface to your volume. Donna On 02/25/2010 03:16 AM, wolf zinke wrote: > Hi, > > I am sorry for this naive an likely many time answered question, but a > first search did not bring up any clear statement to this issue. > > I use caret to view functional data on inflated monkey brains. The data > was analysed with FSL on data oriented according to a coordinate system > based on eye and ear bars, but the caret files use the > anterior,posterior commisure, hence I apply a transformation to my > thresholded functional data (z-values) including a trilinear > interpolation. This of course lead to subthreshold values surrounding > the patches, and reduced, more smooth values within patches. In the step > of mapping the volume data to the surface I again apply > interpolation/averaging of the z-values. > > I am wondering now, if this is an accepted procedure and that the > interpolation of statistical maps is in general not seen as a serious > problem. Though the statistics of the maps are reduced and smeared, I > doubt that this introduces a serious misplacement of the activation > foci. However, I don't fell well to present the range of z-values as > 'z-values' anymore, because of the interpolation. > > I am happy for any pointers regarding such issues. > > thanks, > wolf > > _______________________________________________ > caret-users mailing list > [email protected] > http://brainvis.wustl.edu/mailman/listinfo/caret-users > _______________________________________________ caret-users mailing list [email protected] http://brainvis.wustl.edu/mailman/listinfo/caret-users
